705c53b045
All of the hashing based Map implementations: HashMap, Hashtable, LinkedHashMap, WeakHashMap and ConcurrentHashMap are modified to use an enhanced hashing algorithm for string keys when the capacity of the hash table has ever grown beyond 512 entries. The enhanced hashing implementation uses the murmur3 hashing algorithm along with random hash seeds and index masks. These enhancements mitigate cases where colliding String hash values could result in a performance bottleneck. Reviewed-by: alanb, forax, dl
97 lines
3.7 KiB
Java
97 lines
3.7 KiB
Java
/*
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* Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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* -------------------------------------------
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*
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* Portions Copyright (c) 2010, 2011 IBM Corporation
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*/
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/*
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* @test
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* @bug 6927486
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* @summary A serialized Hashtable can be de-serialized properly.
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* @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
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*/
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import java.io.ByteArrayInputStream;
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import java.io.ByteArrayOutputStream;
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import java.io.ObjectInputStream;
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import java.io.ObjectOutputStream;
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import java.io.PrintWriter;
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import java.io.StringWriter;
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import java.util.Hashtable;
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import java.util.Map;
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public class SimpleSerialization {
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public static void main(final String[] args) throws Exception {
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Hashtable<String, String> h1 = new Hashtable<>();
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System.err.println("*** BEGIN TEST ***");
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h1.put("key", "value");
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final ByteArrayOutputStream baos = new ByteArrayOutputStream();
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try (ObjectOutputStream oos = new ObjectOutputStream(baos)) {
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oos.writeObject(h1);
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}
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final byte[] data = baos.toByteArray();
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final ByteArrayInputStream bais = new ByteArrayInputStream(data);
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final Object deserializedObject;
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try (ObjectInputStream ois = new ObjectInputStream(bais)) {
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deserializedObject = ois.readObject();
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}
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if(!h1.getClass().isInstance(deserializedObject)) {
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throw new RuntimeException("Result not assignable to type of h1");
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}
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if (false == h1.equals(deserializedObject)) {
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Hashtable<String, String> d1 = (Hashtable<String, String>) h1;
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for(Map.Entry entry: h1.entrySet()) {
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System.err.println("h1.key::" + entry.getKey() + " d1.containsKey()::" + d1.containsKey((String) entry.getKey()));
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System.err.println("h1.value::" + entry.getValue() + " d1.contains()::" + d1.contains(entry.getValue()));
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System.err.println("h1.value == d1.value " + entry.getValue().equals(d1.get((String) entry.getKey())));
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}
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throw new RuntimeException(getFailureText(h1, deserializedObject));
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}
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}
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private static String getFailureText(final Object orig, final Object copy) {
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final StringWriter sw = new StringWriter();
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try (PrintWriter pw = new PrintWriter(sw)) {
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pw.println("Test FAILED: Deserialized object is not equal to the original object");
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pw.print("\tOriginal: ");
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printObject(pw, orig).println();
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pw.print("\tCopy: ");
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printObject(pw, copy).println();
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}
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return sw.toString();
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}
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private static PrintWriter printObject(final PrintWriter pw, final Object o) {
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pw.printf("%s@%08x", o.getClass().getName(), System.identityHashCode(o));
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return pw;
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}
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}
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